G. Carl Huber 59 



cle and embracing a tubular segment of variable length, passes between 

 tlie loop of Henle-and the collecting tubule to which said tubule is 

 attached. If one, therefore allows the collecting tubule to which a 

 uriniferous tubule is attached, irrespective of its other relations, to mark 

 the posterior aspect of said tubular configuration, it may be said that the 

 loop of Henle passes down in front of the first part of the proximal convo- 

 luted portion of the tubule, near its origin from the Malpighian corpuscle 

 and this would also assume a position in front of the corpuscle. I can not, 

 therefore, agree with Stoerk when he states, in connection with the state- 

 ment which I have previous!}' quoted (see page 51) in which he refers 

 to the fact that it was not possible to state which of the four or five 

 loops of the secondary S formed the anlage for the loop .of Henle, that — 

 and here I use his own words — " Der Mangel an Gesetzmassigkeit ihrer 

 Bildung aiissert sich auch darin dass sie an zwei zum gleichen Sammelrohr 

 gehorigen Bildungen an der einen vor, an der anderen hinter dem 

 Malpighischen Korperchen herabf alien kann (Model L nnd F aiif der 

 Taf elabbildung) ." Eeference is here made to the downward growth 

 in its development of the loop of Henle. In model L of this' plate, 

 the loop of Henle is well developed and conforms in its relations with 

 those give in my own descriptions of this portion of the uriniferous 

 tubule. The tubule shown in model F of this plate is so little developed 

 that an interpretation of it is not justifiable without seeing the model 

 itself; I will, therefore, not attempt a discussion of it. In all the urinifer- 

 ous tubules reconstructed by me, the loop of Henle is seen to pass down 

 in front of the Malpighian corpuscle or the proximal convoluted tubule 

 in the vicinity of its attachment to the corpuscle — and this applies to the 

 older as well as to the younger developmental stages modeled — if by in 

 front is meant that side of the tubular complex turned away from the 

 collecting tubule to which a uriniferous tubule is attached as explained 

 above and as may be seen from the diagrammatic figures given. 



Differentiation of the Epithelium of the Loop of Henle. 



We ma}'' now return for brief consideration to the stage of development 

 represented by the tubule shown in J of Figs. 3 and 4, representing the 

 oldest stage thus far discussed. This tubule represents one in which the 

 Malpighian corpuscle shows a spherical form and may be regarded as 

 fully developed ; the loop of Henle is clearly recognized and presents the 

 relations described for this portion of the uriniferous tubule, the proximal 

 convoluted portion and about one-half of the proximal or descending 

 limb of Henle's loop show an epithelium with clear protoplasm and 

 nuclei with basal position ; the cells lining the remaining portions of the 



